Thermostatic switch



Oct. 28 1924. 1,513,240

1.. D. HAMMON ET A1.

THERMOSTATIC SWITCH Filed June 6, 1922 l k* I 4 Patented Oct. 28, 1924.

UNITED STATES 1,513,240 `PATENT OFFICE.

LEONARD DOUGLAS EAMMON, 0F BAY OF PLENTY, AND DAVID WILLIAM' MOGILL AND HAROLD BARTLE IRVINE, 0F CHRISTCHURCH, NEW ZEALAND.

THEBMOSTATIC SWITCH.

Application led `Iune 6,

To all whom t `may concern:

Be it lmown that we, LEONARD DOUGLAS HAMMON, DAvn) WILLIAM MCGILL, and HAROLD BARTLE IRVINE, all subjects of the King of Great Britain, residing at King Street, Opotiki, in the Bay of Plenty, in the Dominion of New Zealand, 251 lldgeware Road, Christchurch, in the Domimon of New Zealand, and 34 Latimer Square, Christchurch, aforesaid, respectively, have invented Ynew and useful Improvements in Thermostatic Switches, of which the following is a specification.

This invention relates to electrically heated irons of all kinds and may if desired be applied also to other forms of electrically heated apparatus, the Object of the present invention being to-'provide means whereby the electric circuit in which the heating element is contained, may be automaticall thrown open upon the temperature of such iron or other appliance rising tov a predetermined degree, thus avoiding the dangerous consequences of overheating.

In carrying this object into effect the present invention consists briefly of the provision of a switch inserted in the circuit containing the heating element such switch being adapted to be opened so as to break the said circuitby the operation of an electro-magnetic device the winding of which is included in a relay circuit consisting inthe preferred form of the invention of a shunt oii.' a portion of the heating element, the opening and closing of such relay circuit being efl'ected by the operation of a thermostatic element in response to variations of temperature produced by the said heating element.

The said thermostatic element is necessarily mounted within or upon the structure of the iron or other heating appliance so as to be subject to the thermal influence thereof, while the switch controlling the main circuit, that is to say the circuit con? taining'the heating element, may, together with its said electro-magnetic controlling device be arranged -either upon the said structure or mounted separately as upon a wall or other ixture, in whichfcase the flexible cord for connecting the iron or appli-y ance with the current will contain leads for both the main and relay circuits.

In order thatthe nature of the invention and its construction may be clearly under'- 1922. semi no. 566,352.

stood, reference will now be made to the accompanying sheet of drawings in which Fig. l is a ongitudinal section through an .iron equipped in acordance with the present invention and in which an appropriate position for the switch, if the latter ismounted upon the ii'on, is indicated in dotted lines,

Fig. 2 is a dia ram of the wirin employed in cases W ere the switch a apted to open and close the main circuit is mount-l ed upon the iron,

Fig. 3 is a perspective view showin one practical embodiment of the magnetlcally operated switch employed to control the main circuit, the cover and a ortion of the frame being broken away to c early display the internal parts,

Fig. 4 is a longitudinal section of the solenoid shown in Fig. 3, and,

Fig. 5 is 'a diagram of the wiring employed in cases where the said switch is not mounted upon the iron.

As here shown the invention is a plied to an ordinary well known form ofp elec? trically heated iron comprising a base p0rtion l containing a resistance or element 2 (Figs. 2`and 5), adapted to be heated by the passage therethrough of electric current supplied by means of a main circuit 3, connecting with a suitable source.

To complete the structure the said base is surmounted by a hollow body or cover 4, upon which is carried a suitable handle 5, by means of which the iron is manipulated when in use.

According to the present invention in the circuit 3, is` inserted a switch 6 which may be of any suitable form and adapted, when ,y in the closed condition, to complete such circuit and so sup ly current to the element 2 and when in t e open condition to break such circuit. The said switch is provided .with a handle 7 or other means whereby it through the winding 8 the attraction by the latter of the core 9 will elect the opening of the said switch.

In order to increase this attraction the winding'8 is preferably encased within an iron shell 11 extending around the periphery and one end of such winding while the core 9 is provided with an iron disc or plate '12 adapted toapproach or come in contact `with the open end of said shell when the said movement of the core within the windin takes place.

uitable means are preferably provided for the pur ose of limiting the outward movement o the core 9 away from the winding '8. .As here shown such means comprise lugs or the like 13, formed upon the exterior of the shell 11 and into which lugs are tapped screws 14. By this arrangement the screwslf Imay be so adjusted that their heads will come in contact with the lplate 12 when the latter is in its outward .position 'from the 'winding 8 thereby limiting the extent of such outward movement,

The said winding 8 is inserted in series in a relay'circuit 15 which, in the preferredy form of the' invention, consists, as here shown, of a shunt tapped olf the main circuit 3 and :from the position in such c ircuit to` the inner'or dead -side of the switch 6 in 'order' that the current may 'be disconto a lower potential as desirablefor use in a the rela circuit.

For t e purpose of controlling the open- 'ing and closing of the relay circuit as required for the operation of the invention, a thermostatic element 16 is provided and arranged within the cavity of the cover 4 or at some other portion u on the iron-structure where it will be subJect` to the heat produced by lthe heating `element 2, such thermostatic element being adapted to operate make-and-break contacts arranged inseries -in the relay circuit.

The said thermostatic element consists preferably as here shown of a bi-metallic strip, that is to say a strip composed of two metals having dii'erent Icoeiiicients of expansion and attached together side-by-side throu h-out the length of such strip in order that t e latter will as a whole possess the property of warping or bending in one direction or the other as its temperature rises and falls.

The said strip is rigidly attached at one end as by means of ascrew 17 to the iron structure but. is insulated electrically therefrom, while the other end of such strip is free to move in an upward and downward dirction when its said warping action takes p ace.

Arranged adjacent to the said free end of the strip is a terminal 18, insulated electrically from the iron structure and having a contact point 19 with which a contact point 20 upon the said yfree end of the strip is adapted to make or break electrical connection as such strip warps in response to a rise or fall of temperature. A

The said contacts 19 and 20 are arranged in series with the relay circuit 15 by con# lnecting one end of the latter to the terminal 18' and the other end of the strip 16.

Means of adjustment are also provided in order to enable the said contacts to be sety "to close the relay circuit when a desired degree of temperature has been reached. As here shown` the said means consists of a screw 21 tapped through the terminal` 18 and upon the end of which screw is carried the contact '19, thus by turning the said screw in one direction or the other the said contact 19 will be caused to' approach or recede dfrom the contact '20.

As previously mentioned the switch 6 and its electromagnetic `device may be either mounted upon a convenient portion of the iron structure such, for example, as the position 22 indicated in dotted lines in Fig. 1, or the said devices may be mounted separate from the said structure upon a wall or other convenient fixture.

,In cases where the switch 6 and its controlling electro-magnetic device are mounted upon the iron, or other heating appliance to which the invention isapplied such iron or appliance-will be provided with a plug or other means of connection having two contacts or terminals 23 and 24 to connect the main circuit to a two-wire flexible cord or the like communicating with the current supply as customary.

ln cases where the said switch and its controlling electro-magnetic device are mounted separately from the iron or appliance to which the invention is applied the said plug or means of connection is provided, 1n addition to the said contacts o`r terminals 23 and 24, with a third contact or terminal 25 and a corresponding three-wire cord or conn ction 26Y is. provided in order that current lfrom the'lsupply may be conveyed through the switch 6 by means of the terminals 23 and 24 to the heating element, while the portion of the relay circuit extending between the separately mounted portion of the apparatus and that mounted upon the iron is connected by means of the terminal 25.

In either form of the arangement the operation is as follows The thermostatic element, as previously lSO explained, normally assumes such a position as to separate the contacts 19 and 20 thereby placing the relay circuit l5 in open condition, the electro-magnetic device will therefore be inoperative while such conditions obtain. Upon the switch 6 being closed by hand the main circuit 3 will be completed thereby causing current to flow through the heating element 2 which latter will'thereforeY serve to heat the iron. As the temperature of the iron increases it will have the effect of causing the thermostatic element 16 to warp in such a direction as to carry the contact 2O towards the contact 19 lwhich action results, at a predetermined temperature of the iron, in the establishing of electrical connection between such contacts. This connection of the contacts serves to complete the relay circuit thereby causing current to flow through the coil 8 which therefore becomes energized and attracts the core 9 which latter throu h the connecting rod 10 -serves to open t e switch 6 and so interrupt the liow of current in the main circuit.

If the switch is again closed by hand while the iron remains at the said predetermined temperature, the said means will immediately open such switch.

As the .temperature of the ironfalls however, the thermostatic element 16 will gradually return to its normal condition thereby separating the contacts 19 and 20 and so again opening the relay circuit and rendering the electro-magnetic device inoperative.

We claim:

l. A device of the class described, comprising, in combination, a main circuit, a switch in said circuit. electricallv voperated means for opening said switch, a heating element in said circuit, a thermostatic device within the influence of said heating element a normally open switch in the circuit of said electrically operated means, said thermostatic device being adapted when heated to a predetermined temperature to close said last switch thereby to direct a current through said electrically operated means and cause the same to open the main circuit, and means for retaining said circuit open.

2. A device of the class described, comprising, in combination, a main circuit, a switch in said circuit,'electrically operated means for opening said switch, a heating element in said circuit, a thermostatic devicel within the influence of said heating element, a normally open switch in the circuit of said electrically operated means, said thermostatic device being adapted when heated to a predetermined temperature to close said last switch thereby to direct a current through said electrically operatedmeans and cause the same to open the main circuit, means for retaining said circuit open and 'means for manually closing said circuit` 3. A device of the class described, comprising, in combination, a main circuit, a switch in said circuit, an electromagnet for opening said switch, a normally open relay circuit tapped off said main circuit forsupplying current to said electromagnet, a heat` ing element in the main circuit, a thermostatic device in said relay circuit within the inuence of said heating element and adapted to close the relay circuit when heated to a predetermined temperature thereby to energize said electromagnet and open the main circuit, and a -lever pivotally connected to said main switch and to the core of said magnet and adapted to hold the swtich open after operation of the electroma et, said lever being manually operable into switchclosing position. In testimony whereof we aix our signatures in resence of two witnesses.

LE NARD DOUGLAS HAMMON.

DAVID WILLIAM MGGILL.

HAROLD BARTLE IRVINE.

Witnesses:

CYRIL CARLYN Coa'rns, SIDNEY Jams TRELnAvnN. 

